Timbre (TMI) files are archives consisting of multiple instrument files and used in several Origin games of the early 1990s. The format's creator, Herman Miller, said he thinks TIM was short for Timbre, but couldn't remember for sure. The format stores instrument data for various output devices to work with the game's OMI music files. In the archive, the first file is the system exclusive instruments for the MT-32, the second file contains instruments for AdLib/Sound Blaster, and the third file is unknown, but might be PC Speaker sound effects.

Although the Worlds of Ultima games use the same engine as Ultima VI: The False Prophet (DOS), this new audio format was used instead of the earlier M format. Later Origin games used John Miles's XMI format. Even though the two Ultima VII games used an early version of the Audio Interface Library, and therefore didn't use OMI music, they still made use of TIM instruments for some of their songs.